1. Field of the Invention
The present invention relates generally to gas turbine power plants and more particularly to an arrangement for collecting fluid expelled from bucket tips of a liquid-cooled gas turbine.
2. Description of the Prior Art
It is well known that the efficiency and output of a gas turbine power plant can be improved by increasing the temperature of the hot motive gases and thereby increasing the operating temperature of the turbine. In order to achieve high operating temperatures, it is necessary to provide a means of cooling the most critical turbine components such as the combustion transition members, the turbine nozzles and the turbine buckets. One of the most effective means of cooling the turbine buckets is by supplying liquid coolant to internal passages within the buckets as shown in U.S. Pat. No. 3,446,481 to Kydd and assigned to the assignee of the instant application.
The coolant circulates through the passages in the buckets, transfers heat from the buckets and is then ejected from the open distal end of each bucket. The ejected fluid, consisting of coolant vapor and droplets, if discharged into the flow of hot motive gases, would greatly impair turbine performance and could produce erosion of downstream critical components. Therefore, it is necessary to effectively collect the coolant discharged from the buckets.
The prior art has recognized the necessity to collect the ejected coolant as disclosed in U.S. Pat. No. 3,736,071 to Kydd. In the Kydd structure liquid coolant is received in a collector formed by an open annular slot located within the casing of the turbine. In the U.S. Pat. No. 3,446,481, also to Kydd, ejected coolant is received in a collector formed by annular chamber located within the casing of the turbine.
A problem not solved by the prior art is that of the erosion of the material forming the collector. The coolant is ejected from the distal ends of the turbine buckets at peripheral speeds in excess of 1500 ft. per second. This tangential velocity along with the centrifugal forces on the ejected coolant, propels the coolant at a significant impact force that must be absorbed by the collector.
Another problem associated with an open-chambered collector is that turbulence generated in the collector by the buckets can disrupt the main flow of motive gases through the turbine. Turbulence can also return coolant into the flow of hot motive gases to further impair performance of the turbine.
Accordingly, one object of the invention is to provide an arrangement for more effectively collecting fluid expelled from turbine buckets in a liquid-cooled gas turbine.
Another object of the invention is to provide an arrangement for collecting fluid expelled from a liquid-cooled gas turbine in which the arrangement resists erosion and deterioration by the dynamics of the coolant fluid.
Still a further object of the invention is to provide an arrangement for collecting fluid from a liquid-cooled gas turbine in which the collected fluid is effectively maintained separate from the flow of motive gases.